The purpose of this research program is to determine if differences exist between the dielectric characteristics of normal and neoplastic tissues and to provide basic data for a number of normal and neoplastic tissue types over the 0.01 GHz to 10.0 GHz frequency range. Ultimately, the goal is to employ this dielectric property information in the design of electromagnetic (EM) illumination systems which use to maximum advantage any characteristic differences in the dielectric properties of normal and neoplastic tissues to produce optimal heating of malignancies. The proposed research to be performed during this research project includes (1) measurements of the in-vivo dielectric properties of several different tumor lines in mice, (2) in-vivo measurements of normal canine tissues (muscle, fat, kidney, liver, brain), (3) probe dielectric measurements of normal tissues and surface lesions in human volunteers, an (4) evaluation of the data to determine if significant differences in tissue properties exist to enable the design of suitable EM illuminators for effective hyperthermia treatment.